~2/3 (approximately two-thirds) unitless
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||"Indels are seen along the evolutionary history of every protein family, and are often the driving force for the acquisition of new functions and structures (Pikkemaat and Janssen, 2002 Park et al., 2006). Insertions-by-duplication seem to play a special role, as approximately two-thirds of insertions observed in natural genomes are of this type (primary sources)."